Sometimes it's as simple as going to the file's properties in your preferred file manager and ticking the Write box. However, as your error seems to indicate a read only file system, I assume the stick itself hadn't mounted properly, that's a bit odd, presumably after you pulled it and reinserted it, it remounted rw, as one would expect.

Something like that. I did reach from my little CLI book, but it's not there. I think it's in the loft and I left the Fedora based Linux guide down here instead. The book isn't in plain English. It's like "Man pages - the full volume!"

I have "Linux Command: Instant Reference" which is a bit like that, but it's one short reach from my desk. And much better than "Linux Complete", which is basically just all of man from a particular era in print.

It said read-only filesystem, not read-only file, so chmod won't help. In fact it won't do anything because the filesystem is read-only. This is not unusual with USB sticks and is usually caused by a filesystem error causing the kernel to mount the stick read-only to prevent damage. Unmounting and remounting the stick generally works, unless the filesystem is already damaged.

"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)